From d77972ab601eac1ca1f7ba2498e4f878c590b534 Mon Sep 17 00:00:00 2001
From: Rune <rune@rune-90X3A.(none)>
Date: Thu, 22 Sep 2011 09:21:00 +0200
Subject: [PATCH] added customErrorMessage to Yesod.Form.Functions to allow the
 user to overwrite the parse-error messages on fields.

---
 yesod-form/Yesod/Form/Functions.hs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/yesod-form/Yesod/Form/Functions.hs b/yesod-form/Yesod/Form/Functions.hs
index b5910e4e..f762b621 100644
--- a/yesod-form/Yesod/Form/Functions.hs
+++ b/yesod-form/Yesod/Form/Functions.hs
@@ -31,6 +31,7 @@ module Yesod.Form.Functions
     , check
     , checkBool
     , checkM
+    , customErrorMessage
     ) where
 
 import Yesod.Form.Types
@@ -309,3 +310,8 @@ checkM f field = field
             Right Nothing -> return $ Right Nothing
             Right (Just a) -> fmap (either (Left . SomeMessage) (Right . Just)) $ f a
     }
+
+-- | Allows you to overwrite the error message on parse error.
+customErrorMessage :: SomeMessage master -> Field sub master a -> Field sub master a
+customErrorMessage msg field = field { fieldParse = \ts -> fmap (either
+(const $ Left msg) Right) $ fieldParse field ts }